Near-field scanning optical microscopy to study nanometric structural details of LiNbO3 Zn-diffused channel waveguides

Abstract

A near-field scanning optical microscope ͑NSOM͒ is used to perform structural and optical characterization of the surface layer after Zn diffusion in a channel waveguide fabricated on lithium niobate. A theoretical approach has been developed in order to extract refractive index contrast from NSOM optical transmission measurements ͑illumination configuration͒. As a result, different solid phases present on the sample surface can be identified, such as ZnO and ZnNb 2 O 6 . They appear like submicrometric crystallites aligned along the domain wall direction, whose origin can be ascribed to some strain relaxation mechanism during the annealing process after Zn diffusion.

Near-Field Scanning Optical Microscopy Applied to the Study of Ferroelectric Materials

“…5c. Therefore the optical contrast can be directly interpreted by means of geometrical considerations (Canet-Ferrer et al, 2008). Unfortunately, dielectric profile usually presents a Gaussian shape at the ferroelectric domain walls and consequently the effective dielectric constant cannot be determined by means of Eq.…”

“…For instance, in Ref. (Canet-Ferrer et al, 2008) we simulated the refractive index contrast produced by solid phases present on the surface of a channel waveguide in lithium niobate. In that case, the presence of the waveguide was considered by introducing an additional layer.…”